Non-invasive silicon temperature measurement by infrared transmission for rapid thermal processing applications

A method for the noninvasive measurement of silicon wafer temperature based on infrared transmission is presented. The method is well suited to the 400-800°C temperature range, can be used through thick quartz walls, and is compatible with rapid thermal processing and epitaxial growth. The approach relies on the decreased bandgap, higher phonon population, and increased free carrier concentrations in silicon at elevated temperatures. These effects cause increased optical absorption in the infrared (near band-edge) region due to both increased band-to-band and intraband absorption. By measuring the infrared optical transmission of the wafer in situ during processing, an intimate measure of the wafer temperature can be attained. Improved control of silicon-germanium film growth has been demonstrated